Re: [PATCH net-next v9] virtio/vsock: replace virtio_vsock_pkt with sk_buff

From: Paolo Abeni <pabeni@redhat.com>
To: Bobby Eshleman <bobby.eshleman@bytedance.com>
Cc: Bobby Eshleman <bobbyeshleman@gmail.com>,
	Cong Wang <cong.wang@bytedance.com>,
	Stefano Garzarella <sgarzare@redhat.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next v9] virtio/vsock: replace virtio_vsock_pkt with sk_buff
Date: Tue, 10 Jan 2023 15:45:32 +0100	[thread overview]
Message-ID: <5042e5c6e57a3f99895616c891512e482bf6ed28.camel@redhat.com> (raw)
In-Reply-To: <91593e9c8a475a26a465369f6caff86ac5d662e3.camel@redhat.com>

On Tue, 2023-01-10 at 09:36 +0100, Paolo Abeni wrote:
> On Sat, 2023-01-07 at 00:29 +0000, Bobby Eshleman wrote:
> > This commit changes virtio/vsock to use sk_buff instead of
> > virtio_vsock_pkt. Beyond better conforming to other net code, using
> > sk_buff allows vsock to use sk_buff-dependent features in the future
> > (such as sockmap) and improves throughput.
> > 
> > This patch introduces the following performance changes:
> > 
> > Tool/Config: uperf w/ 64 threads, SOCK_STREAM
> > Test Runs: 5, mean of results
> > Before: commit 95ec6bce2a0b ("Merge branch 'net-ipa-more-endpoints'")
> > 
> > Test: 64KB, g2h
> > Before: 21.63 Gb/s
> > After: 25.59 Gb/s (+18%)
> > 
> > Test: 16B, g2h
> > Before: 11.86 Mb/s
> > After: 17.41 Mb/s (+46%)
> > 
> > Test: 64KB, h2g
> > Before: 2.15 Gb/s
> > After: 3.6 Gb/s (+67%)
> > 
> > Test: 16B, h2g
> > Before: 14.38 Mb/s
> > After: 18.43 Mb/s (+28%)
> > 
> > Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
> > Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
> > Acked-by: Paolo Abeni <pabeni@redhat.com>
> > ---
> > 
> > Tested using vsock_test g2h and h2g.  I'm not sure if it is standard
> > practice here to carry Acks and Reviews forward to future versions, but
> > I'm doing that here to hopefully make life easier for maintainers.
> > Please let me know if it is not standard practice.
> 
> As Jakub noted, there is no clear rule for tag passing across different
> patch revisions.
> 
> Here, given the complexity of the patch and the not trivial list of
> changes, I would have preferred you would have dropped my tag.
> 
> > Changes in v9:
> > - check length in rx header
> > - guard alloactor from small requests
> > - squashed fix for v8 bug reported by syzbot:
> >     syzbot+30b72abaa17c07fe39dd@syzkaller.appspotmail.com
> 
> It's not clear to me what/where is the fix exactly, could you please
> clarify?

Reading the syzkaller report, it looks like iov_length() in
vhost_vsock_alloc_pkt() can not be trusted to carry a reasonable value.

As such, don't you additionally need to ensure/check that iov_length()
is greater or equal to sizeof(virtio_vsock_hdr) ?

Thanks.

Paolo